The days may be numbered for soda-slurping tourists in flip-flops who enjoy parking their sport utility vehicles under the giant sequoias of Yosemite and tromping around in human herds amid theme-park-style trams, car exhaust and noise.

The National Park Service on Tuesday released its long-awaited environmental review of plans to restore the Mariposa Grove of Giant Sequoias to something closer to its natural state — that is, without the indecorous carnival hubbub.

The document, which is open for review and public comment through May 7, proposes the removal of a gift shop and parking lot in the middle of the towering trees, the elimination of the trams, construction of a boardwalk over restored habitat and wetlands, new hiking trails and shuttle buses from a remote location.

“This will really help because right now there is a lot of congestion and there is not enough parking for everybody,” said Sue Beatty, a restoration ecologist at Yosemite National Park. “The goal is to protect the trees into the future, to preserve the whole grove and the habitat of the giant sequoias while really allowing people to come in and have a quality visitor experience.”

The Mariposa Grove, near the south entrance to the park, is famous for its massive trees, many of which approach 300 feet in height. The 484 ancient trees are not as tall as coastal redwoods, but their trunks are generally thicker. The reigning king of these fabled trees is the 100-foot circumference Grizzly Giant, which has been estimated to be as old as 2,700 years. Its branches are thicker than the trunks of most trees.

Another featured attraction at the grove is the California Tunnel Tree, which draws hordes of folk who get their thrills walking through a hole carved through the trunk in 1895. It wasn’t the first California redwood to be used this way. Historic photographs still circulate depicting carriages and early automobiles driving through the Wawona Tunnel Tree, which was carved out in 1881. It provided amusement for the masses until the weakened tree toppled over in 1969. The dead giant is still lying in Mariposa Grove, but it has been renamed “the Fallen Tunnel Tree.”

The problem now, according to Beatty, is that giant sequoia roots, which extend out 200 feet, are shallow, only going down five or six feet into the soil. A huge increase over the past few decades in the number of visitors to the grove has put stress on the trees, she said — tourists have been trampling the roots.

Beatty said park biologists are concerned that future climate change could combine with the car exhaust and other pollutants coming from the asphalt parking lot and further harm the trees.

The park’s draft Environmental Impact Statement proposes four alternatives to the way things are now, including its shortest and least-expensive proposal, which is to do nothing. The rejected ideas include continuing the open-air trams, which wind along a narrow road through the trees and include recorded narration at a cost of about $25 per person. Another proposal is to build a parking lot and road leading to the Grizzly Giant.

The preferred alternative, which is expected to cost about $15 million, paid mostly by the nonprofit Yosemite Conservancy, would remove 115 parking spaces that now sit in the middle of the grove, something the park’s general management plan proposed as far back as 1980.

A new lot would be built two miles away from the grove, at the south entrance of Yosemite, where free shuttles would be provided. A trail would also be built from the entrance to the grove for those who prefer walking. Only motorists with disability placards would be allowed to drive up to the sequoias, where limited parking would be available near the Grizzly Giant.

Native vegetation would be planted, a boardwalk trail would be built and a half-mile handicap- accessible loop trail would be built through the lower grove.

“What we would like to do is restore wetlands and hydrology and soils within the grove so that the trees can regenerate,” Beatty said. “By removing some of the infrastructure, we are opening up more giant sequoia habitat … and providing trails for people to walk on so they are not damaging the roots of the trees.”

Assuming all goes as planned, groundbreaking will begin in 2014, the 150-year anniversary of the date the grove was preserved by the Yosemite Grant, which was signed by President Lincoln in 1864, at the height of the Civil War.

“The Mariposa Grove is one of the icons of the park service,” said Beatty, who said she has yet to encounter opposition to the plan, which is an attempt to create a place “where people will have a more reverential experience.”